Can I save presets for the inset tool?
No there is no way save for scripting to load and save presets for operators that do not explicitly support it in the toolbar. This would not be my recommendation for a first project in blender API however after a few basic tutorials (maybe this ) you should be able to do this sort of thing on your own.

Edit: Another alternative that comes to my mind is duplication. I can't tell if that is helpful but certainly making one bolt by hand is far easier than making a script to do it.